linux-kernel - Re: [PATCH v6 13/18] perf: add support for taken branch sampling to perf report

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Message-ID: <CABPqkBTufRUjVN_0v3h7RfcFmmO4h4N04wb0ypP5jq22UbYV4w@mail.gmail.com>
Date:	Thu, 23 Feb 2012 21:48:38 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Roberto Agostino Vitillo <ravitillo@....gov>,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	robert.richter@....com, ming.m.lin@...el.com, andi@...stfloor.org,
	asharma@...com, vweaver1@...s.utk.edu, khandual@...ux.vnet.ibm.com,
	dsahern@...il.com
Subject: Re: [PATCH v6 13/18] perf: add support for taken branch sampling to
 perf report

On Thu, Feb 23, 2012 at 7:11 PM, Arnaldo Carvalho de Melo
<acme@...hat.com> wrote:
> Em Thu, Feb 23, 2012 at 05:53:53PM +0100, Stephane Eranian escreveu:
>> Ok, so I looked at that today. Adding the feature bit is trivial.
>> But what's not easy is to get to the feature bit in perf report
>> by the time we need it. Very quickly after parsing the options,
>> we setup a bunch of things such as browser mode, sorting
>> order based on the -b option. But to get to the feature bit, we
>> would need to wait until after the session is created in
>> __cmd_report() which is way later.
>>
>> So we either hoist perf_session__new() very early, i.e., as soon
>> as we have the filename or we write yet another parse_header()
>> function just to get to the feature bits. I would rather choose the
>> first option. But none is really pretty...
>>
>> Arnaldo, any better idea?
>
> Humm, lemme see...
>
>
> By the time we need it is when we do setup_sorting, right? Perhaps we
> can delay that till after we do perf_session__new and thus have read the
> headers...
>
Well, there is also the UI setup (use_stdio setup_browser and the likes).
Then, yes, it's sorting.

> /me looks at the code.
>
> - Arnaldo
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